Messages in this thread Patch in this message |  | | Subject | Re: [PATCH v3 0/5] Improve newidle lb cost tracking and early abort | From | Tim Chen <> | Date | Fri, 29 Oct 2021 10:00:40 -0700 |
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On Wed, 2021-10-27 at 10:49 +0200, Vincent Guittot wrote: > > > Few problems still remain in your case if I'm not wrong: > There is a patch that ensures that rq->next_balance is never set in > the past. >
Vincent,
Were you planning to take the patch to prevent the next_balance to be in the past?
Tim
--- From 2a5ebdeabbfdf4584532ef0e27d37ed75ca7dbd3 Mon Sep 17 00:00:00 2001 From: Tim Chen <tim.c.chen@linux.intel.com> Date: Tue, 11 May 2021 09:55:41 -0700 Subject: [PATCH] sched: sched: Fix rq->next_balance time updated to earlier than current time To: hmem@eclists.intel.com
In traces on newidle_balance(), this_rq->next_balance time goes backward and earlier than current time jiffies, e.g.
11.602 ( ): probe:newidle_balance:(ffffffff810d2470) this_rq=0xffff88fe7f8aae00 next_balance=0x1004fb76c jiffies=0x1004fb739 11.624 ( ): probe:newidle_balance:(ffffffff810d2470) this_rq=0xffff88fe7f8aae00 next_balance=0x1004fb731 jiffies=0x1004fb739 13.856 ( ): probe:newidle_balance:(ffffffff810d2470) this_rq=0xffff88fe7f8aae00 next_balance=0x1004fb76c jiffies=0x1004fb73b 13.910 ( ): probe:newidle_balance:(ffffffff810d2470) this_rq=0xffff88fe7f8aae00 next_balance=0x1004fb731 jiffies=0x1004fb73b 14.637 ( ): probe:newidle_balance:(ffffffff810d2470) this_rq=0xffff88fe7f8aae00 next_balance=0x1004fb76c jiffies=0x1004fb73c 14.666 ( ): probe:newidle_balance:(ffffffff810d2470) this_rq=0xffff88fe7f8aae00 next_balance=0x1004fb731 jiffies=0x1004fb73c
It doesn't make sense to have a next_balance in the past. Fix newidle_balance() and update_next_balance() so the next balance time is at least jiffies+1. --- kernel/sched/fair.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1d75af1ecfb4..740a0572cbf1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9901,7 +9901,10 @@ update_next_balance(struct sched_domain *sd, unsigned long *next_balance) /* used by idle balance, so cpu_busy = 0 */ interval = get_sd_balance_interval(sd, 0); - next = sd->last_balance + interval; + if (time_after(jiffies+1, sd->last_balance + interval)) + next = jiffies+1; + else + next = sd->last_balance + interval; if (time_after(*next_balance, next)) *next_balance = next; @@ -10681,6 +10684,8 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf) out: /* Move the next balance forward */ + if (time_after(jiffies+1, this_rq->next_balance)) + this_rq->next_balance = jiffies+1; if (time_after(this_rq->next_balance, next_balance)) this_rq->next_balance = next_balance; -- 2.20.1
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